Border Buddy

Answer the three questions every international trip actually depends on — Do I need a visa? Is my passport valid enough? What can I bring through customs? — plus the one people always get wrong: how long can I legally stay? (the Schengen 90/180 trap).

Overview

border-buddy combines an embedded rules engine (visa policy snapshots, passport validity rules, health certificate requirements, customs allowances for ~50 countries) with a precise Schengen 90/180-day rolling-window calculator. It turns "I'm a Brazilian passport holder flying to Portugal via Frankfurt for 6 weeks" into a structured entry-readiness report — before you book non-refundable tickets.

The scripts run fully offline on an embedded knowledge snapshot. Immigration rules change — always pair this skill with a live check of the destination's official immigration site (the report includes the right authority to verify with, per country).

When to Use

• User asks: "do I need a visa for X?", "how long can I stay in Europe?", "is my passport valid for Japan?"
• Planning any international itinerary with connections (transit visa checks are the #1 surprise)
• Counting Schengen days across a multi-trip year — the rolling window defeats manual counting
• Checking what can be carried through customs: alcohol, tobacco, cash (the €10,000 / $10,000 declaration threshold)
• Verifying vaccination certificate needs (yellow fever is the big one for Africa/South America routes)

Don't use for: asylum/immigration-law advice, work-permit or residency applications, or anything involving criminal-record entry waivers (ETA/ESTA eligibility denials) — those need official channels or a lawyer. This is trip-planning intelligence, not legal advice.

How It Works

1. Load nationality + destinations (IATA-style country codes or names).
2. Visa matrix lookup — each destination has a policy table keyed by nationality group: visa_free, visa_on_arrival, eta, evisa, visa_required, plus max stay days and notes.
3. Passport validity check — applies the 6-month rule (or the country-specific exceptions) against the passport expiry date; flags the "3-month + valid-for-stay" Schengen nuance.
4. Health rules — yellow fever certificate required if coming from (or transiting through) an endemic country; lists the relevant endemic set.
5. Customs snapshot — duty-free alcohol/tobacco allowances and the cash-declaration threshold for the destination.
6. Transit checks — every layover country over the airside-transit threshold gets its own visa row (China, UK, US, Canada, Australia require transit visas for many nationalities).
7. Schengen calculator (separate command) — reads a visit log (JSON/CSV), computes the rolling 180-day window from any reference date, and reports days used / remaining / overstay warnings.

Quick Start

# Entry-readiness report for a trip
python3 scripts/border_buddy.py check \
  --nationality BR --destination PT \
  --transit DE --stay-days 42 --purpose tourism \
  --passport-expiry 2027-03-01

# How many Schengen days do I have left after this year's trips?
python3 scripts/border_buddy.py schengen --visits visits.json --on 2026-09-15

# See it work end-to-end with built-in sample data
python3 scripts/border_buddy.py demo

# List every country rule in the snapshot
python3 scripts/border_buddy.py rules --destination JP

Steps (Agent Workflow)

1. Collect: nationality, destination(s), transit point(s), trip purpose, dates, passport expiry. (Transits are optional but ask — most surprises live there.)
2. Run check with what you have; the report flags every missing input that matters.
3. If any destination is Schengen and the user travels repeatedly, run schengen with their visit history.
4. Read the report back to the user with the verification links/authorities listed — never present the snapshot as guaranteed-current.
5. If a rule looks stale (snapshot includes as_of dates), do a live web check of the official source and reconcile.

Output Shape

ENTRY READINESS ─ Portugal (PT) for BR nationals
  Visa:         NOT REQUIRED (Schengen 90/180) ✓
  Max stay:     90 days in any 180-day window
  Passport:     VALID — expires 2027-03-01, must be valid 3 mo beyond
                departure and issued within 10 years ✓
  Transit DE:   AIRSIDE TRANSIT OK (no visa) ✓
  Yellow fever: not required (not arriving from endemic country)
  Customs:      1L spirits / 4L wine · cash > €10,000 must be declared
  VERIFY WITH:  sef.pt (Serviço de Estrangeiros e Fronteiras)

Common Pitfalls

1. Counting Schengen days with a calendar app. The 90/180 rule is a rolling window — the day you leave doesn't count as a stay day, and old trips fall out of the window mid-trip. Use the calculator; manual counting is how people get 5-year bans.
2. Forgetting transit visas. A 3-hour layover in London (LHR) or Toronto (YYZ) still requires a transit visa for many nationalities. Always pass --transit.
3. Trusting the 6-month rule everywhere. Some countries require 6 months validity, others only "valid for the duration of stay". The rules table encodes per-country requirements — don't apply one rule globally.
4. Treating the snapshot as live law. Visa policy changed weekly somewhere in the world since this snapshot's as_of date. The report always names the official source to verify against — show it to the user.
5. Confusing visa-free stay length with the Schengen allowance. e.g., Americans get 90 days in Portugal under the PT rule but it's the same 90/180 pool as the rest of Schengen. Multi-destination European trips must be budgeted from one pool.
6. Purpose changes everything. "Tourism" answers don't apply to work, study, or paid performances. Always confirm purpose before answering.

Verification Checklist

• Nationality and every destination (including transits) passed as ISO codes or names
• Passport expiry checked against the destination's specific validity rule
• Schengen destinations cross-checked with schengen if the user has prior visits
• Report shown with "verify with" authorities — never as a guarantee
• Purpose of travel confirmed (tourism vs work/study changes visa class)

One-Shot Recipes

"I'm Indian, flying Delhi → Paris in May, 10 days, passport expires November"

python3 scripts/border_buddy.py check --nationality IN --destination FR \
  --stay-days 10 --purpose tourism --passport-expiry 2026-11-30
# → visa required (Schengen short-stay), passport OK but tight, apply ≥3 weeks out

"How many days can I still spend in Europe this year?"

python3 scripts/border_buddy.py schengen --visits my_visits.json --on 2026-10-01
# → days used, days remaining, date the oldest trip exits the window

References

• references/visa-rules.md — how the policy matrix is structured, nationality groups, transit rules
• references/schengen-180.md — the 90/180 algorithm, worked examples, common edge cases